I own and shoot the sigma 9mm. I purchased it more as a demo for my CHL students to shoot. It has a double action only trigger. Students need to shoot both single action and double action semi-autos. If you don't mind a long heavy trigger pull the sigma is a fine first gun. You will probably want something sexier down the road. The more you practice with its heavy trigger the tighter your groups will become.
It's easy to clean and fires every time you load it and pull the trigger.
The Sigma has been considered a "problem" for S&W by many. The newer M&P's are fine guns and recently had a $50. rebate. Check them before you buy. I got an M&P compact this spring, traded in a Glock 27 (never liked geometry of grip - but very small), H & K P2000 compact (sharper recoil) and a Sig 230 (only a .380). (Other gun purchase with trades) Even the dealer had a M & P for his personal carry. I consider the M&P for my smallest concealable as I have other handguns for vehicles etc. Beretta Storms in 4" are also nice, but I did not care for the compacts.
The first generation Sigmas are widely regarded as junk. A poor attempt at copying the Glock.
The later generation Sigmas are the red-headed stepchild of the pistol world. They're still a poor copy of the Glock, but with the M&P (a good copy of a Glock), one has to wonder what the purpose of the Sigma is in the world. It would appear that S&W keeps it around simply to offer a basement-priced polymer wonder gun. Most of the Sigmas I've seen around have not aged well, but for the price of dinner out with the family, it might be worth having around, however, I would not have one as a carry gun or a nightstand gun. Can't say why - just that I wouldn't. I have Glocks for that purpose.
My brother bought one three years ago when Gander had them for 299 + 50 rebate and two spare mags. I shot it and it goes bang every time, BUT, you have to use both fingers to pull the trigger. It sucks. Stay away. Find a used glock. I bought a Walther PPS .40 S&W and love it.
My brother bought one brand new in 40 S&W(an early gun), and we had a hell of a time with both reloads and factory loads. Finally, S&W agreed with the results of our troubleshooting - insufficient headspace - the chamber was not reamed deep enough. They replaced the barrel.
It still is very finicky it is only reliable with RN FMJ ammo. Most everything else, including factory TC and JHP jam it.
I would steer clear of these POS and purchase a Glock, Sig. etc. There's a reason that they're pretty much giving Smegmas away...
There's a pretty easy fix for the Sigma triggers. I believe there are 2 springs in the trigger mechinisim and you remove one. I've seen it on a couple of discussion boards. S&W will work on the trigger for you if you send it in.
My buddy has a .40 Sigma. He treats it like a rented mule. I doubt that he's ever cleaned it. He's used to the 10lb trigger and shoots it damn well. He got his for $299 less the rebate. For $250 it's a heck of a gun IMO.
I bought the Fullsize 9mm and one in 40 S&W years ago when they first came out. S&W was nice enough to "fix" the triggers on both of them while they were in to have the sights set to print on paper. They both had point of aim issues, but the 40 was off the paper. I got them back and they were on the money and the triggers were much improved with regards to smoothness, but still a bit heavy. The triggers are very consistent and not bad once you get used to them. I also have another one that was set up with a barrel for 357 Sig. Same work on the trigger. The triggers are very looooooooong and heavy. The cost of these was a little over half the cost of a Glock at the time. If I were looking for a primary gun, I'd buy a Glock 23 or a Sig P229 in 40 s&w. I will say that the Sigmas will shoot rather decent groups at 25 yards and they have never skipped a beat. They digest almost anything you feed them without a hitch. They had a mini Sigma at one time also. Would I spend $350 for one with a LaserLyte? I doubt I would, since I can get a better firearm for just a little more, although without the Laserlyte. I have under $700 total invested in all three of mine, but those were mid 1990's dollars.
They originally came out with the "Full" capacity magazines, but the ASS Weapons ban cut them to ten rounds. I bought a crapload of spare full cap magazines for a good price, before they went up in price.
In thinking about your question since my first post, what do you plan to do with the Sigma? If you're thinking defense, spend enough to rely on it. Many guns shoot most the time, not good enough if your life depends on it.
More importantly, choose based on the way it fits your hand! I have had and sold many fine guns, once I realized they were not suited to me, my fit. With some knowledge and practice, shooting your handgun should be almost instinctive. If you can't "get into the grove", it may not be right for you. Many newer polymer models have adjustable grips, a real asset.
Springfield XDm 40. I can feed mine anything. Not one malfunction in my first 500 rounds. Very nice trigger. I like it so much I bought a Surefire X300 light for it and it is now my home defense gun. Speer 180 Gold Dot HP ammo is very accurate.